1. Field of the Invention
The invention relates to a mountable contact element for a tube of an electrically nonconductive material, which has an encompassing external electrically conductive coating as its electrode.
2. Prior Art
In certain technical applications, the problem arises of establishing a mountable, mechanically stable and electrically very highly conductive, high-voltageproof contact means with an electrode that is mounted as an electrically conductive encompassing external coating on a tube of an electrically nonconductive material, especially glass or glass ceramic.
One such application is for instance in a tube ozonizer of the kind described in German Patent Disclosure DE 195 11 001 A1. The following demands are made of a contacting means for such externally coated glass cylinders that are used as ozone tubes:
high ozone resistance PA1 high voltage strength PA1 low transfer resistance between contact and glass tube despite great roughness of the conductive glass coating PA1 contacting over the entire circumference of the cylinder in the contact region PA1 firm mechanical seat on the glass tube PA1 minimal external dimensions PA1 assurance that neither the coating nor the glass can be damaged when the contact is being assembled PA1 lowest possible expense for assembly and disassembly.
In other applications, comparable demands must be met. The aforementioned German patent disclosure does not show any constructively specific embodiment of a contact element that would meet the above demands.
In particular the demand for low transfer resistance precludes the conventional contacting means, such as contacts in the form of sleeves that surround the region to be contacted in jacket-like fashion.
One such contacting means has become known for instance from German Patent Disclosure DE 26 06 731 B2, which discloses a tubular ozone generator with an external electrode, preferably in the form of a metal foil on a glass tube. This external electrode is surrounded by an axially segmented outer jacket. The segments are held together by clamping devices, which press the external electrode onto the glass tube and also press the external jacket onto the external electrode. One pole of the high-voltage source is then connected to this outer jacket. It is impossible in principle to create a continuous areal contact between the outer jacket and the external electrode in this way.